[Desire HD Q&A, Help & Troubleshooting] sashank:
How long a time approximately? All ROMs take a bit of time on first boot. This is when they're populating the dalvik-cache with optimized data for each app on the phone. So it's normal to see a black screen or continuous bootanimation for some time on first boot. So once you flash a ROM, just let your phone be idle till it turns on fully. Don't pull battery or do anything in between. The next time you reboot your phone, you'll see that it boots much faster because the dalvik-cache is already built.

Coming to the topic of the ROM you're trying to flash, ViperSaga is a ROM for the HTC Desire S, not the Desire HD. You shouldn't be flashing it. Even if it was a ROM for the DHD, you need to flash the ROM zip first and *then* flash the OTA. OTA = Over The Air. OTA zip files are meant for small updates to an already existing ROM. They are not the full ROM, so you need to flash the full ROM first and then flash the OTA package to update it. These OTAs can also be downloaded in Settings->About->System software updates.

In the 4th post in the ViperSaga thread, a list of ROM downloads is provided. The actual ROM file is ViperSAGA v1.0.0 (dev-host) which is 427.47 MB. That is the one that should be flashed first. The OTA file is meant to bump the ROM from v1.0.0 to v.1.1.0, not to be flashed by itself. That's why it's of such a small size of 28.47 MB. ROMs are never that small a size.

Now, DON'T flash that ROM. It's not meant for this phone! If you want a similar ROM, there's ViperDHD by the same developer. And don't flash gapps for a ROM unless it's explicitly mentioned in the first post of the ROM thread. If you look throught the cfX and JellyTime threads, you'll see that it is. You will find the latest gapps (Android version-specific) at http://goo.im/gapps and you can read about gapps at http://wiki.rootzwiki.com/Google_Apps.

The reason you weren't able to see the options for full wipe and the modifications is because, apart from flashing a wrong device ROM firstly, you didn't flash the right ROM file, so the AROMA installer didn't show up. AROMA is an interactive installer that allows you to choose stuff rather than just directly flashing a ROM file. Try the same procedure with ViperDHD, following the instructions and downloading the right files, and you'll see everything properly. ViperDHD has an AROMA installer that provides options to wipe your phone automatically rather than doing it yourself, thus making it easier to flash the ROM. ROMs don't usually have this. Before flashing a new ROM (not an update to an already flashed ROM, but an entirely new one), you should ALWAYS wipe your phone fully. This can be done in recovery by going to 'wipe & format' and choosing 'wipe boot', 'wipe system', 'wipe data/factory reset' and 'wipe cache'. For example, if you want to switch from ViperDHD to cfX, then you need to full wipe. If you just want to flash an updated version of ViperDHD or cfX, then you don't need to unless you're testing for bugs to report to the developer.

Here are some guides to booting into recovery and the correct flashing procedure of a ROM -

http://xdaforums.com/showthread.php?p=35937493

http://xdaforums.com/showpost.php?p=30530565&postcount=179

I'm not sure about your internet issue, but first flash that ROM and try if it works.